Inter-halogen compounds, with

Most double bonds are easily halogenated ° with bromine, chlorine, or inter-halogen compounds.Substitution can compete with addition in some cases.lodination has also been accomplished, but the reaction is slower. Under free-radical conditions, iodination proceeds more easily. " However, vic-diiodides are generally unstable and tend to revert to iodine and the alkene. 

Infrared spectroscopy has assisted in the determination of the structure of certain complex inorganic molecules, uch as the metal carbonyls, inter-halogen compounds, boron hydrides, and nitrogen oxides. The practice used has been to compare the observed spectrum with the spectrum expected for an assumed model on the basis... 

Pyridines react easily with halogens and inter-halogens to give crystalline compounds, largely undissociated when dissolved in solvents such as carbon tetrachloride. Structurally they are best formulated as resonance hybrids related to trihalide anions. 1-Fluoropyridinium triflate is also crystalline and serves as an electrophilic fluorinating agent (31.1). ... 

The halogens form covalent compounds with most of the nonmetallic elements (including each other) and the metalloids. These compounds are usually molecular substances, with the relatively low melting points and boiling points characteristic of substances with small forces of inter-molecular attraction. 

The halogen chlorides are of course limited to those of Br and I, but although BrCl exists in equilibrium with Cl2 and Br2, it is so unstable that it is not obtained in a pure form. Iodine monochloride is a much more stable compound that exists in two forms. The a form consists of ruby-red needles, and the (3 form is a reddish-brown solid. The forms differ in the way that IC1 molecules are linked by inter-molecular forces in the solid state. 

Non-tetrahedral structures of organic derivatives of the silicon subgroup elements are often caused by inter- or intra-molecular coordination interaction X M. This takes place in compounds where there is a nucleophilic substituent at the central M atom. An electronegative X atom, which has at least one unshared electron pair (X = N, P, O, S, halogen) and is directly bonded to M, can be such a substituent. Compounds of this kind tend to be involved in inter-molecular coordination. There can be also a heteroatom X as part of the organic substituent at M in this case an intra-molecular coordination usually occurs . Such compounds, which contain five- or six-membered coordination rings, include, for example, draconoides (4) , their analogues (5) , metalloatranes (6) and others. The stability of a coordination bond X —> M increases with the atomic number of M Si < Ge < Sn < Pb. 

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